Strike-slip 23 January 2018 MW 7.9 Gulf of Alaska rare intraplate earthquake: Complex rupture of a fracture zone system.

Krabbenhoeft, Anne, von Huene, Roland, Miller, John J., Lange, Dietrich and Vera, Felipe (2018) Strike-slip 23 January 2018 MW 7.9 Gulf of Alaska rare intraplate earthquake: Complex rupture of a fracture zone system. Open Access Scientific Reports, 8 (13706). DOI 10.1038/s41598-018-32071-4.

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Abstract

Large intraplate earthquakes in oceanic lithosphere are rare and usually related to regions of diffuse deformation within the oceanic plate. The 23 January 2018 MW 7.9 strike-slip Gulf of Alaska earthquake ruptured an oceanic fracture zone system offshore Kodiak Island. Bathymetric compilations show a muted topographic expression of the fracture zone due to the thick sediment that covers oceanic basement but the fracture zone system can be identified by offset N-S magnetic anomalies and E-W linear zones in the vertical gravity gradient. Back-projection from global seismic stations reveals that the initial rupture at first propagated from the epicenter to the north, likely rupturing along a weak zone parallel to the ocean crustal fabric. The rupture then changed direction to eastward directed with most energy emitted on Aka fracture zone resulting in an unusual multi-fault earthquake. Similarly, the aftershocks show complex behavior and are related to two different tectonic structures: (1) events along N-S trending oceanic fabric, which ruptured mainly strike-slip and additionally, in normal and oblique slip mechanisms and (2) strike-slip events along E-W oriented fracture zones. To explain the complex faulting behavior we adopt the classical stress and strain partitioning concept and propose a generalized model for large intra-oceanic strike-slip earthquakes of trench-oblique oriented fracture zones/ocean plate fabric near subduction zones. Taking the Kodiak asperity position of 1964 maximum afterslip and outer-rise Coulomb stress distribution into account, we propose that the unusual 2018 Gulf of Alaska moment release was stress transferred to the incoming oceanic plate from co- and post-processes of the nearby great 1964 MW 9.2 megathrust earthquake.

Document Type: Article
Additional Information: Original seismic and multibeam bathymetric data are available at http://walrus.wr.usgs.gov. Gravity data are available at http://topex.ucsd.edu.
Keywords: Geodynamics, Natural hazards, Seismology, Tectonics
Research affiliation: OceanRep > The Future Ocean - Cluster of Excellence > FO-R03
OceanRep > The Future Ocean - Cluster of Excellence
GFZ
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: 10.1038/s41598-018-32071-4
ISSN: 2045-2322
Related URLs:
Projects: Future Ocean
Date Deposited: 19 Sep 2018 10:01
Last Modified: 24 May 2019 08:57
URI: http://oceanrep.geomar.de/id/eprint/44294

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